A bag contains $3$ red marbles, $4$ green marbles, and $8$ blue marbles. If a marble is randomly chosen, what is the probability that it is not green?
Explanation: There are $3 + 4 + 8 = 15$ marbles in the bag. There are $4$ green marbles. That means $15 - 4 = 11$ are not green. The probability is $ \frac{11}{15}$.